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Hydraulic circuit having a rotary type pump and brake apparatus for a vehicle provided with the same |
| 6474751 |
Hydraulic circuit having a rotary type pump and brake apparatus for a vehicle provided with the same
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| Patent Drawings: | |
| Inventor: |
Yamaguchi, et al. |
| Date Issued: |
November 5, 2002 |
| Application: |
09/694,680 |
| Filed: |
October 24, 2000 |
| Inventors: |
Abe; Yoichi (Kariya, JP)
Fuchida; Takeshi (Kariya, JP)
Mori; Hideshi (Chiryu, JP)
Morikawa; Toshiya (Kariya, JP)
Sato; Takashi (Okazaki, JP)
Sawada; Mamoru (Yokkaichi, JP)
Yamaguchi; Takahiro (Kariya, JP)
Yonemura; Shuichi (Anjo, JP)
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| Assignee: |
Denso Corporation (Kariya, JP) |
| Primary Examiner: |
Graham; Matthew C. |
| Assistant Examiner: |
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| Attorney Or Agent: |
Harness, Dickey & Pierce, PLC |
| U.S. Class: |
303/116.4; 418/171 |
| Field Of Search: |
303/116.4; 418/171; 418/129; 418/166; 418/112; 418/125; 418/126; 418/131; 418/134; 418/133; 418/136; 418/139; 418/140; 418/206.6; 418/218; 418/149; 418/190; 418/55.4 |
| International Class: |
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| U.S Patent Documents: |
4453782; 4580847; 5064254; 5158343; 5169214; 5236256; 5261730; 5281012; 5322363; 5342120; 5350224; 5350225; 5367942; 5374112; 5383719; 5383720; 5393131; 5401083; 5405191; 5427442; 5445441; 5445444; 5487597; 5492394; 5496099; 5544947; 5586814; 5727852; 5779328; 5882091; 5961188; 5947566; 5967626; 5967628; 5273527; 6270169 |
| Foreign Patent Documents: |
1800633; 4205041; 4338906; 4438966; 4427246; 4438721; 0253157; 0798187; 2653725; 22882649; 2 297 134; 54-77316; 54-162207; 55-025621; 58-59359; 59-045256; 60-85284; 61-155687; 61-287850; 62-270750; 63-62859; 1-257658; 7-76267; 4-087868; 4-121260; 5-78792; 5-86442; 5-170074; 5-92483; 6-032212; 7-54050; 7-076267; 8-121365; 8-128392; 8-144964; 8-159044; 8-230634; 8-291793; 9-296250; 10-176219; 11-222627; WO 95/19282; WO 96/10507 |
| Other References: |
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| Abstract: |
In the brake apparatus having a rotary pump, outer and inner rotors of the rotary pump are made of bearing steel and inner and outer teeth portions of the rotors are respectively processed by nitriding hardening or carbo-nitriding hardening. Accordingly, outer circumferential region of the outer teeth portion and inner circumferential region of the inner teeth are constituted by nitrided layer containing 15 to 40 percents retained austenite so that teeth faces of the outer and inner teeth portions in mesh may have higher wear resistance. |
| Claim: |
What is claimed is:
1. A brake apparatus having a master cylinder, wheel cylinder and a rotary pump for supplying brake fluid to the wheel cylinder so as to more increase brake fluid pressure inthe wheel cylinder than that in the master cylinder, the rotary pump comprising: first and second rotors made of bearing steel each having teeth portions at least at one of inner and outer peripheries thereof; and a plurality of gaps formed between theteeth portions of the first and second rotors which are in mesh with each other, brake fluid being sucked into and discharged from the gaps according to rotations of the first and second rotors, wherein the first and second rotors have circumferentialsurfaces of the teeth portions which are respectively processed by at least one of nitriding hardening and carbo-nitriding hardening so that nitrogen is diffused into the first and second rotors to form a layer including CrN.
2. A brake apparatus having a master cylinder, wheel cylinder and a rotary pump for supplying brake fluid to the wheel cylinder so as to more increase brake fluid pressure in the wheel cylinder than that in the master cylinder, rotary pumpcomprising: a casing having intake and discharge ports; an outer rotor having inner teeth portions at inner periphery thereof; an inner rotor having outer teeth portions at outer periphery thereof, the inner and outer rotors being housed in the casingso as to constitute a plurality of gaps formed between the inner and outer teeth portions which are in mesh with each other and the gaps being communicated with the intake and discharge ports; and a drive shaft for driving the inner rotor in the casing,brake fluid being sucked from the intake port and, via the gaps, discharged from the discharge port according to a rotation of the drive shaft, wherein the outer and inner rotors are made of bearing steel and have circumferential surfaces of the innerand outer teeth portions which are respectively processed by at least one of nitriding hardening and carbo-nitriding hardening so that nitrogen is diffused into the first and second rotors to form a layer including CrN.
3. A brake apparatus according to claim 2, wherein each of the circumferential surfaces of the teeth portions is provided with nitrided layer having 15 to 40 percents retained austenite.
4. A brake apparatus according to any one of claims 1 to 3, further comprising; a main conduit communicating brake fluid of the master cylinder to the wheel cylinder; and an auxiliary conduit bypassing the main conduit, wherein the rotary pumpdisposed in the auxiliary conduit for sucking brake fluid from the auxiliary conduit on a side of the master cylinder and discharging the same to the auxiliary conduit on a side of the wheel cylinder so that brake fluid pressure of the wheel cylinder maybe more increased than that of the master cylinder. |
| Description: |
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brake apparatus provided with a rotary type pump in particular, having an internal gear pump such as a trochoid pump for sucking and discharging fluid and a method of manufacturing the same.
2. Related Arts
An internal gear rotary pump such as a trochid pump and the like is constituted by an inner rotor having outer teeth portion at an outer periphery thereof, an outer rotor having inner teeth portion at an inner periphery thereof, and a casing forcontaining the outer and inner rotors. The inner rotor and the outer rotor are arranged in the casing in a state where the inner and outer teeth portions are in mesh with each other and a plurality of gaps are formed by the respective teeth portions.
When a line running on respective central axes of the outer and inner rotors is defined as a centerline of the pump, an intake port and a discharge port, which communicate with the plurality of gaps, respectively, are formed on both sides of thecenterline. When the pump is driven, the inner rotor rotates with the central axis as a drive axis. In accordance therewith, the outer rotor also rotates in the same direction as the inner rotor by mesh between the outer and inner teeth portions. Inthis case, each of the gaps changes from a large volume to a small volume and vice versa during a time period in which the outer rotor and the inner rotor make one turn. Due to that volume change, fluid is sucked from the intake port and discharged tothe discharge port.
Conventionally, to cope with wear and tear of the outer and inner rotors in the rotary pump mentioned above, the rotors are made of sintered material, the rotors made of sintered material are processed by carburising, the rotor are made ofbearing steel or the rotors made of bearing steel are processed by quenching and tempering. However, when the rotary pump is used in the brake apparatus, processing the rotors through the carburising treatment mentioned above is not sufficient to securehigh wear resistance required for the rotors since lubricity of brake fluid is low so that very high pressure occur on teeth faces of the rotors that are meshed with each other (in particular, at portions where the gap has a maximum volume). Further,the rotors may be made of tool steel such as SKH or SKD, which has higher wear resistance.
However, the tool steel is expensive and has poor forgeability. Furthermore, the rotors made of tool steel containing higher carbide content for enhancing the wear resistance is likely to crack at the portions of the carbide so that the rotorsmay not have sufficient strength. Moreover, the rotors made of conventional sintered material can't have sufficient fatigue strength because of voids.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a brake apparatus having a rotary type pump in which outer and inner rotors has higher wear resistance at the teeth faces where the rotors are meshed with each other.
To achieve the object mentioned above, the brake apparatus has a rotary pump comprising first and second rotors made of bearing steel each having teeth portions at least at one of inner and outer peripheries thereof, and a plurality of gapsformed between the teeth portions of the first and second rotors which are in mesh with each other so that brake fluid may be sucked into and discharged from the gaps according to rotations of the first and second rotors. With the rotary pump, the firstand second rotors have circumferential surfaces of the teeth portions which are respectively processed by at least one of nitriding hardening and carbo-nitriding hardening.
Further, it is preferable that the rotary pump has a casing having intake and discharge ports, outer and inner rotors having inner and outer teeth portions at inner and outer peripheries thereof, respectively, so that the inner and outer rotorsare housed in the casing so as to constitute a plurality of gaps formed between the inner and outer teeth portions which are in mesh with each other and the gaps are communicated with the intake and discharge ports, and a drive shaft for driving theinner rotor in the casing so that brake fluid may be sucked from the intake port and, via the gaps, discharged from the discharge port according to a rotation of the drive shaft.
With the rotary pump mentioned above, the outer and inner rotors are made of bearing steel and have circumferential surfaces of the inner and outer teeth portions that are respectively processed by at least one of nitriding hardening andcarbo-nitriding hardening.
Furthermore, each of the circumferential surfaces of the teeth portions is provided, preferably, with nitrided layer having 15 to 40 percents retained austenite.
Moreover, in a brake apparatus having a main conduit communicating brake fluid of a master cylinder to a wheel cylinder and an auxiliary conduit bypassing the main conduit, the rotary pump may be disposed in the auxiliary conduit for suckingbrake fluid from the auxiliary conduit on a side of the master cylinder and discharging the same to the auxiliary conduit on a side of the wheel cylinder so that brake fluid pressure of the wheel cylinder may be more increased than that of the mastercylinder.
Another object of the present invention is to provide a method of manufacturing outer and inner rotors of the rotary pump in which outer and inner rotors has higher wear resistance at the teeth faces where the rotors are meshed with each otherand has mirror finished surfaces at side surfaces of the rotors so as to limit brake fluid leakage between the side surfaces of the rotor and side plates of a casing.
To achieve the object mentioned above, in the rotary pump having inner and outer rotors provided with outer and inner teeth portions, respectively, which are contained in a center bore of a center plate so as to make the outer and inner teethportions in mesh with each other and are put between first and second side plates, the method of manufacturing the outer and inner rotors comprises steps of, at first, forming the outer and inner teeth portions at inner and outer peripheries of pipemembers made of bearing steel, respectively, then, executing at least one of nitriding and carbo-nitriding on the respective pipe member, then, cutting the respective pipe member into a small pieces to constitute a plurality of the respective outer andinner rotors, next quenching and tempering the outer and inner rotors, and, finally, executing mirror-like finishing on cutting faces of the outer and inner rotors.
With the steps mentioned above, mirror-like finished surfaces of the outer and inner rotors may face the first and second side plates, while teeth faces of the teeth portions in mesh are covered by nitrided layer containing 15 to 40 percentretained austenite.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects, features and characteristics of the present invention will be appreciated from a study of the following detailed description, the appended claims, and drawings, all of which form a part of this application. In thedrawings:
FIG. 1 is a model diagram indicating a first embodiment according to the present invention;
FIG. 2A is a drawing indicating detailed structure of a holding device in the first embodiment;
FIG. 2B is a graph illustrating characteristic of the holding device;
FIG. 3A is a drawing indicating detailed structure of a modification of the holding device;
FIG. 3B is a graph illustrating characteristic of the modification of the holding device;
FIG. 4A is a drawing indicating detailed structure of an another modification of the holding device;
FIG. 4B is a graph illustrating characteristic of the another modification of the holding device;
FIG. 5A is a drawing indicating detailed structure of the other modification of the holding device;
FIG. 5B is a graph illustrating characteristic of the other modification of the holding device;
FIG. 6 is a structural view indicating a second embodiment of the present invention;
FIG. 7 is a structural view indicating a third embodiment of the present invention;
FIG. 8 is a modification of a brake-fluid amplifying device in the third embodiment;
FIG. 9 is a drawing indicating a modification of the pressure-amplifying device;
FIG. 10 is a structural view indicating a fourth embodiment of the present invention;
FIG. 11 is a structural view indicating a fifth embodiment of the present invention;
FIG. 12 is a structural view indicating a sixth embodiment of the present invention;
FIG. 13 is a flowchart indicating control content of the sixth embodiment;
FIG. 14 is a time chart illustrating control result according to the sixth embodiment;
FIG. 15 is a modification of the flowchart according to the sixth embodiment;
FIG. 16 is a structural view indicating a seventh embodiment of the present invention;
FIGS. 17A and 17B are explanatory diagrams indicating states of pressure applied to wheel cylinders;
FIG. 18 is a structural view indicating a eighth embodiment of the present invention;
FIG. 19 is a structural view indicating a ninth embodiment of the present invention;
FIGS. 20A and 20B are explanatory diagrams indicating states of pressure applied to wheel cylinders;
FIG. 21 is a structural view indicating a tenth embodiment of the present invention;
FIG. 22 is a graph indicating change in brake-fluid pressure according to the tenth embodiment;
FIG. 23 is a structural view indicating an eleventh embodiment of the present invention;
FIG. 24 is a graph indicating change in brake-fluid pressure according to the eleventh embodiment;
FIG. 25 is a structural view indicating a twelfth embodiment of the present invention;
FIG. 26 is a block diagram indicating an electrical control unit of the twelfth embodiment;
FIG. 27 is a flowchart indicating control processing of the twelfth embodiment;
FIG. 28 is a structural view indicating a thirteenth embodiment of the present invention;
FIG. 29 is a structural view indicating the fourteenth embodiment of the present invention;
FIG. 30 is a structural view indicating the fifteenth embodiment of the present invention;
FIG. 31 is a structural view indicating the sixteenth embodiment of the present invention;
FIG. 32 is a block diagram indicating an electrical control unit of the sixteenth embodiment;
FIG. 33 is a flowchart indicating control processing of the sixteenth embodiment;
FIG. 34 is a structural view indicating a seventeenth embodiment of the present invention;
FIG. 35 is a structural view indicating operation of an brake control apparatus according to the seventeenth embodiment;
FIG. 36 is a block diagram indicating an electrical control unit of the seventeenth embodiment;
FIG. 37 is a flowchart indicating control processing of the seventeenth embodiment;
FIG. 38 is a structural view indicating an eighteenth embodiment of the present invention;
FIG. 39 a block diagram indicating an electrical control unit of the eighteenth embodiment;
FIG. 40 is a flowchart indicating control processing of a nineteenth embodiment;
FIGS. 41A and 41B are explanatory diagrams indicating a starting criterion of the nineteenth embodiment;
FIGS. 42A to 42C are graphs indicating an experimental result according to the nineteenth embodiment;
FIG. 43 is a flowchart indicating control processing of a twentieth embodiment;
FIG. 44 is an explanatory diagram indicating a starting criterion of the twentieth embodiment;
FIG. 45 is a flowchart indicating control processing of a twenty-first embodiment;
FIG. 46 is a flowchart indicating control processing of a twenty-second embodiment;
FIGS. 47A and 47B are characteristic diagrams indicating a mode of operation of the twenty-second embodiment;
FIG. 48 is a flowchart indicating control processing of a twenty-third embodiment;
FIG. 49 is a characteristic diagram indicating a mode of operation of the twenty-third embodiment;
FIG. 50 is a structural view indicating a structure of a brake control apparatus according to a twenty-fourth embodiment;
FIG. 51 is a flowchart according to the twenty-fourth embodiment;
FIG. 52 is an explanatory diagram indicating an effect of a twenty-fifth embodiment;
FIG. 53 is a structural view indicating a brake control apparatus of the twenty-fifth embodiment and a peripheral structure thereof;
FIG. 54 is a block diagram indicating a structure of an electronic control unit of the twenty-fifth embodiment;
FIGS. 55A and 55B are explanatory diagrams indicating actuation of valves in a vacuum booster shown in FIG. 54;
FIG. 56 is a flowchart indicating control processing of the control unit of the twenty-fifth embodiment;
FIGS. 57A to 57H are time charts indicating operation of the brake control apparatus of the twenty-fifth embodiment;
FIGS. 58A and 58B are schematic structural views indicating a vacuum booster of a twenty-sixth embodiment; and
FIG. 59 is a structural view indicating a modification of the seventeenth embodiment;
FIG. 60A is a model diagram indicating a brake system including a rotary type pump according to a twenty-seventh embodiment of the present invention;
FIG. 60B is a diagram indicating an electronic control unit for ABS control;
FIG. 61 is a drawing indicating detailed structure of a pump unit 10 in the twenty-seventh embodiment;
FIG. 62A is a sectional view of the rotary type pump 40 of the twenty-seventh embodiment;
FIG. 62B is a sectional view taken on line LXIIB--LXIIB in FIG. 62A;
FIG. 63 is a drawing indicating detailed structure of a pump unit 10 in a twenty-eighth embodiment;
FIG. 64A is a sectional view of the rotary type pump 40 of the twenty-eighth embodiment;
FIG. 64B is a sectional view taken on lime LXIVB--LXIVB in FIG. 64A;
FIG. 65 is a drawing indicating detailed structure of a pump unit 10 in a twenty-ninth embodiment;
FIG. 66A is a model diagram indicating a brake system including a rotary type pump according to a thirtieth embodiment of the present invention;
FIG. 66B is a diagram indicating an electronic control unit for ABS control and brake assist control;
FIG. 67A is a sectional view of a rotary type pump according to a thirty-first embodiment;
FIG. 67B is a sectional view taken on line LXVIIB--LXVIIB in FIG. 67A; and
FIG. 68 is a diagram indicating a comparison of wear amounts between rotors processed by carbo-nitriding hardening treatment and rotors not processed by the carbo-nitriding hardening treatment.
DETAILED DESCRIPTION OF THE PREFERREDEMBODIMENTS
A first embodiment of a brake control apparatus according to the present invention will be described hereinafter with reference to the drawings.
FIG. 1 is a structural view indicating the first embodiment according to the present invention. In the first embodiment, the brake control apparatus is applied in a vehicle of a diagonal brake-fluid conduit system provided with respectivebrake-fluid conduits of connecting front-right wheel cylinder with rear-left wheel cylinder and connecting front-left wheel cylinder with rear-right wheel cylinder in a front-wheel drive four-wheeled vehicle.
In FIG. 1, a brake pedal 1 depressed by a driver when applying braking force to the vehicle is connected to a booster 2, and depression force applied to the pedal 1 and pedal stroke thereof are conveyed to this booster 2. The booster 2 has atleast two chambers, a first chamber and a second chamber, and for example the first chamber can be set as an atmospheric-pressure chamber and the second chamber can be set as a vacuum chamber. Intake-manifold vacuum of an engine, vacuum generated by avacuum pump or the like is employed as the vacuum introduced in the vacuum chamber. Accordingly, this booster 2 directly boosts the driver's pedal depression or pedal stroke by a pressure differential of the atmospheric-pressure chamber and the vacuumchamber. The booster 2 has a push rod or the like to convey the depression force or pedal stroke boosted in this way to a master cylinder 3, and this push rod generates master-cylinder pressure PU by compressing a master piston disposed on the mastercylinder 3. The master cylinder 3 is provided with an independent master reservoir 3a to supply brake fluid to the master cylinder 3 or to accumulate excess brake fluid from the master cylinder 3.
In this way, an ordinary vehicle is provided with the brake pedal 1, booster 2, master cylinder 3, and so on as a brake-fluid pressure-generating device for imparting braking force to the vehicle body.
The master-cylinder pressure PU generated in the master cylinder 3 is conveyed to brake fluid within a first conduit A linking the master cylinder 3 and a first wheel cylinder 4 disposed in the front-right wheel FR to impart braking force to thiswheel, and the master 3 and a second wheel cylinder 5 disposed in the rear-left wheel RL to impart braking force to this wheel. The master-cylinder pressure PU is similarly conveyed also to a second conduit linking respective wheel cylinders disposed inthe front-left wheel and the rear-right wheel to the master cylinder 3. However, because structure similar to the first conduit A can be employed, detailed description will be omitted.
The first conduit A is made up from two parts separated by a pressure-amplifying device 10 disposed in this first conduit A. That is to say, the first conduit A has a first conduit part A1 to receive the master-cylinder pressure PU in theinterval from the master cylinder 3 to the pressure-amplifying device 10 and a second conduit part A2 in the interval from the pressure-amplifying device 10 to the several wheel cylinders 4 and 5.
The pressure-amplifying device 10 moves brake fluid of the first conduit part A1 to the second conduit part A2 and holds the pressure at the second conduit part A2 at second brake-fluid pressure PL when the pedal 1 is depressed and themaster-cylinder pressure PU is generated within the first conduit A. According to this first embodiment, this pressure-amplifying device 10 is made up of a holding device 13 and a pump 15 which will be described later. Additionally, in the structure ofthe first conduit A, the first conduit part A1 is formed between the holding device 13 and the master cylinder 3 as well as the pump 15 and the master cylinder 3. The second conduit part A2 is formed between the several wheel cylinders 4 and 5 andholding device 13 as well as the several wheel cylinders 4 and 5 and the pump 15. Furthermore, a normal proportioning control valve 6 as well-known is disposed at the second conduit part A2 to operate so that the brake-fluid pressure applied to thesecond wheel cylinder 5 on the rear-left wheel RL side becomes smaller than the brake-fluid pressure (i.e., the master-cylinder pressure PU) applied to the first wheel cylinder 4 on the front-right wheel FR. This normal proportioning control valve 6 isprovided to prevent the rear wheel, as far as is possible, from falling into a locking state earlier than the front wheel in a case where load movement of the vehicle or the like has occurred during vehicle braking, but elimination is also possible.
The pump 15 is connected within the first conduit A in parallel with the holding device 13, and takes in brake fluid from the first conduit part A1 and discharges brake fluid to the second conduit part A2 during generation of the master-cylinderpressure PU. That is to say, the pump 15 and the holding device 13 are structured as an example of a brake-fluid moving device to move the brake fluid in the first conduit part A1 to the second conduit part A2 when the master-cylinder pressure PU hasbeen generated.
A plunger pump utilized in an ordinary antiskid apparatus or the like may be employed as this pump 15, or a compressor or the like may be employed as the pump 15. Additionally, the pump 15 may be constantly driven during generation of themaster-cylinder pressure PU, or may be driven in accordance with for example pedal depression force, pedal stroke of the brake pedal 1 or the master-cylinder pressure PU. Additionally, the pump 15 may be driven by a motor (not illustrated) utilized inan ordinary antiskid apparatus or the like.
In a case where brake fluid has been moved from the first conduit part A1 to the second conduit part A2 by the pump 15 and the brake-fluid pressure of the second conduit part A2 has become the second brake-fluid pressure PL which is greater thanthe master-cylinder pressure PU, the holding device 13 acts to maintain this differential pressure (PL-PU). In a case where the driver's foot has been removed from the brake pedal 1 and the master-cylinder pressure PU has been released, it is preferredthat the brake fluid which had been applying the second brake-fluid pressure PL to the wheel cylinders 4 and 5 be returned to the master cylinder 3 side. At this time, the brake fluid may be returned through this holding device 13, or the brake fluidmay be returned by detecting that the pedal 1 has entered a nondepressed state on a basis of output from a brake switch or the like, and changing a two-way valve or the like connected in parallel to the holding device 13 from an interrupted state to acommunicated state.
In this way, the pressure-amplifying device 10 provided with the pump 15 and the holding device 13 moves the brake fluid of the first conduit part A1 which has assumed the same pressure as the master-cylinder pressure PU accompanying depressionof the brake pedal 1 to the second conduit part A2, reduces the brake-fluid pressure within the first conduit part A1, i.e., the master-cylinder pressure PU. The pressure-amplifying device 10 simultaneously maintains the differential pressure of theamplified second brake-fluid pressure PL within the second conduit part A2 and the master-cylinder pressure PU. The pressure-amplifying device 10 performs pressure amplification in this way.
The second brake-fluid pressure PL which has been caused to be greater than the master-cylinder pressure PU is applied to the several wheel cylinders 4 and 5, so that high braking force is ensured.
A mode of operation according to the brake apparatus structured as was described above will be described hereinafter.
The pump 15 is driven when master-cylinder pressure PU has been generated during vehicle braking. The brake fluid at the first conduit part A1 is moved to the second conduit part A2 due to the drive of the pump 15. As a result, themaster-cylinder pressure PU is reduced, and increase in master-cylinder pressure PU is suppressed even in a case where the driver has depressed the pedal 1 still more forcefully. Accordingly, reaction force transmitted to the driver through the pedal 1is lessened by the master-cylinder pressure PU not becoming excessively great. Accordingly, the load for generating master-cylinder pressure PU by the driver can be alleviated, and the load applied to the master cylinder 3 and the like to generate themaster-cylinder pressure PU also can be alleviated. Accordingly, the master-cylinder pressure PU is suppressed as was described above, but simultaneously the brake-fluid pressure applied to the wheel cylinders 4 and 5 is increased by thepressure-amplifying device 10 as the brake-fluid moving device. Therefore, vehicle braking force can sufficiently be ensured.
Because pressure amplification of the second conduit part A2 is performed utilizing the brake fluid within the first conduit part A1, the brake-fluid quantity returned to the master cylinder 3 from the first conduit A when the driver has releasedthe pedal 1 comes to be equivalent to the brake-fluid quantity originally introduced into the first conduit A from the master cylinder 3. Accordingly, return of brake fluid to the master cylinder 3 also can be realized without providing excessive brakefluid to the master cylinder 3.
A specific structure and mode of operation of the above-described holding device 13 will variously be indicated hereinafter with reference to FIG. 2A through FIG. 5B.
FIG. 2A is an example of structure of the holding device 13 employing a proportioning control valve (P valve).
As shown in FIG. 2A, the proportioning control valve 13 is connected in reverse at the location of the holding device 13 in FIG. 1. The proportioning control valve 13 ordinarily acts to convey basic pressure of the brake fluid to a downstreamside while attenuating the brake-fluid pressure with a predetermined attenuation ratio when the brake fluid is flowing in a normal direction. Accordingly, when the proportioning control valve 13 is connected in reverse as shown in FIG. 2 A, the secondconduit part A2 side comes to generate the foregoing basic pressure and the first conduit part A1 side becomes the downstream side when the brake fluid flows from the second conduit part A2 to the first conduit part A1 through the proportioning controlvalve 13. Accordingly, as shown in FIG. 2B, in a case where the brake-fluid pressure PL within the second conduit part A2 has become not less than split-point pressure P1 established for the proportioning control valve 13 accompanying increase in thebrake-fluid quantity within the second conduit part A2 due to the drive of the pump 15, the second brake-fluid pressure PL within the second conduit part A2 is conveyed to the first conduit part A1 in accordance with the slope of line Y2, i.e., thepredetermined attenuation ratio. Accordingly, when the master-cylinder pressure PU in the first conduit part A1 is seen as a reference, the second brake-fluid pressure PL increased by discharge of the pump 15 due to this proportioning control valve 13comes to be held in a state amplified in an inverse relationship with the above-described predetermined attenuation ratio. Additionally, because brake-fluid pressure corresponding to the brake-fluid pressure of the second conduit part A2, i.e., thesecond brake-fluid pressure PL, is held within the first conduit part A1 as well, a suitable master-cylinder pressure PU can be assured even if the pump 15 should be driven excessively. Accordingly, an abnormal decline in the brake-fluid pressure of thefirst conduit part A1, i.e., the master-cylinder pressure PU, and occurrence of an abnormal increase in the stroke of the pedal 1 and a no-load state of pedal reaction force can be prevented.
The master-cylinder pressure PU declines when depression of the pedal 1 by the driver has weakened. However, at this time, the second brake-fluid pressure PL also declines through the proportioning control valve 13 accompanying the decline inthe master-cylinder pressure PU. Thus, brake operation that gives high regard to the intention of the driver can be obtained. As is understood from FIG. 2B, in a state where the second brake-fluid pressure PL has a smaller brake-fluid pressure than thesplit-point pressure P1 of the proportioning control valve 13, the second brake-fluid pressure PL is in a state of having passed through the proportioning control valve 13 and been released to the first conduit part A1 side. Consequently, nodifferential pressure is established between the first conduit part A1 and the second conduit part A2. Additionally, because the second brake-fluid pressure PL is adjusted in accordance with the master-cylinder pressure PU when the second brake-fluidpressure PL is smaller than the split-point pressure P1, no differential pressure is established between the master-cylinder pressure PU and the second brake-fluid pressure PL. That is to say, in a case where the master-cylinder pressure PU or thesecond brake-fluid pressure PL is smaller than the split-point pressure P1, a relationship between the master-cylinder pressure PU and the second brake-fluid pressure PL in FIG. 2B comes to accord with line X2 indicating that this relationship is one toone.
Accordingly, by setting the split-point pressure P1 of the proportioning control valve 13 to a pressure which is high to a certain extent, the second brake-fluid pressure PL applied to the wheel cylinders 4 and 5 can be increased in comparisonwith the master-cylinder pressure PU only in a case where high braking force is required and the brake pedal 1 has been forcefully depressed.
When the split-point pressure P1 has been established at 0, a differential pressure is ensured so that the second brake-fluid pressure PL is unfailingly increased with respect to the master-cylinder pressure PU and the second brake-fluid pressurePL becomes greater than the master-cylinder pressure PU when brake fluid is moved by the pump 15.
In a case where brake fluid flows from the first conduit part A1 to the second conduit part A2 through the proportioning control valve 13, brake-fluid pressure similar to the basic pressure is conveyed to the downstream side without performingattenuation of the brake-fluid pressure. According to this embodiment, the basic-pressure side of the proportioning control valve 13 is the first conduit part A1 side, and the downstream side is the second conduit part A2 side. That is to say, a casewhere brake fluid flows from the master cylinder 3 side to the wheel cylinder 4 and 5 side corresponds. Accordingly, when the proportioning control valve 13 is connected in reverse as shown in FIG. 2A, as in this embodiment, at least the master-cylinderpressure PU can be applied to the wheel cylinders 4 and 5 even if a situation should occur wherein the master-cylinder pressure PU cannot be increased to the second brake-fluid pressure PL due to faulty drive or the like of the pump 5.
When the proportioning control valve 13 is employed as the holding device in this way, not only can a pressure-amplifying operation of the brake-fluid pressure applied to the several wheel cylinders 4 and 5 be realized with the mechanicalstructure, but because the foregoing split-point pressure P1 may be established as a matter of mechanical design, pressure-amplifying operation which accords with the intention of the driver can be realized with substantially no electrical control. Forexample, pressure-amplifying operation is not realized when the master-cylinder pressure PU is not more than the split-point pressure P1, even when pump drive is started in accompaniment with depression of the brake pedal 1 and the pump 15 is drivenconstantly during vehicle braking. That is to say, when the value of the split-point pressure P1 is established at a master-cylinder pressure PU whereat it can be estimated that the brake pedal 1 has been forcefully depressed and the driver requireslarge braking force, pressure-amplifying operation is executed and brake assistance can be realized with no electrical control when the master-cylinder pressure PU has risen to this split-point pressure P1 or more. Furthermore, there exists theadvantage that it is sufficient to utilize a brake switch or the like already ordinarily provided on the vehicle in determination of execution of pump drive, with no need to add sensor components, complex control, or the like.
A load-sensing proportioning valve as well-known may be utilized as the proportioning control valve 13. In this case, it is possible to vary the amplifying effect of the second brake-fluid pressure, i.e., the split-point pressure P1, incorrespondence with vehicle weight which changes according to loaded weight and so on.
Next, mode of operation and effects when employing a two-way valve 131 having a port having a differential-pressure valve and a port to realize a communicated state as the holding device 13 in FIG. 1 will be described utilizing FIGS. 3A and 3B.
When a needle valve of the two-way valve 131 is moved and the two-way valve 131 takes a position as shown in FIG. 3A in a case where the brake pedal 1 is depressed and the master-cylinder pressure PU is generated, flow of brake fluid from thefirst conduit part A1 side to the second conduit part A2 side is prohibited. In contrary, flow of brake fluid in the direction from the second conduit part A2 to the first conduit part A1 is permitted in a case where differential pressure of the secondbrake-fluid pressure PL at the second conduit part A2 and the master-cylinder pressure PU at the first conduit part A1 has reached a predetermined value. Accordingly, when the pump 15 has been driven, differential pressure between the second brake-fluidpressure PL at the second conduit part A2 and the master-cylinder pressure PU at the first conduit part A1 is maintained to a predetermined pressure. The second brake-fluid pressure PL which is higher than the master-cylinder pressure PU (shown by aline X3 in FIG. 3B) by a value corresponding to the predetermined pressure is applied to the several wheel cylinders 4 and 5, as shown by a line Y3 in FIG. 3B.
When braking operation by the driver has finished, the two-way valve 131 is switched to a communicated state and the brake fluid establishing the second brake-fluid pressure PL is released to the master cylinder 3 side.
A check valve 134 is connected in parallel to the two-way valve 131. This check valve 134 allows flow of brake fluid from the first conduit part A1 to the second conduit part A2. Accordingly, the second brake-fluid pressure PL is maintained, asit is higher than the master cylinder pressure PU even in a case where the second brake-fluid pressure PL has been increased with respect to the master-cylinder pressure PU. At least the master-cylinder pressure PU can be assured to be applied to thewheel cylinders 4 and 5 due to the check valve 134 being connected in this way, even if a problem that the two-way valve 131 is held at the valve position of the differential-pressure valve should occur or a faulty drive of the pump 15 should occur.
Next, mode of operation and effects in a case where a restrictor 132 is employed as the holding device 13 will be described with reference to FIGS. 4A and 4B.
When the restrictor 132 is disposed in the first conduit part A1 as shown in FIG. 4A, the brake-fluid pressure of the second conduit part A2 can be caused to be brake-fluid pressure (the second brake-fluid pressure) which is higher than themaster-cylinder pressure PU within the first conduit part A1 due to flow resistance of the restrictor 132 when brake fluid within the first conduit part A1 is moved to the second conduit part A2 by the pump 15.
In this case, it is possible to increase the second brake-fluid pressure PL at a certain uniform ratio with respect to the master-cylinder pressure PU, as shown by a line Y4 in FIG. 4B, according to the drive method of the pump 15. That is tosay, when the pump 15 is driven at a uniform discharge capacity, the characteristic indicated by line Y4 in FIG. 4B can be exhibited. Additionally, when the pump 15 is driven after the brake-fluid pressure of either the master-cylinder pressure PU orthe second brake-fluid pressure PL has reached a predetermined pressure P1, without driving the pump 15 until the brake-fluid pressure of either the master-cylinder pressure PU or the second brake-fluid pressure PL becomes the predetermined pressure P1,the characteristic of a line Z4 or line W4 in FIG. 4B can be obtained. The characteristic of line Z4 or the characteristic of line W4 can be obtained by varying the discharge capacity of the pump 15.
Next, mode of operation and effects will be described when employing a two-way valve 133 provided merely with an interrupted position and a communicated position as the holding device 13, as shown in FIGS. 5A and 5B.
When the pump 15 is driven after generation of the master-cylinder pressure PU, assurance of differential pressure of the second brake-fluid pressure PL and the master-cylinder pressure PU is realized by interrupting the flow of brake fluidbetween the first conduit part A1 and the second conduit part A2 by this two-way valve 133 as shown in FIG. 5A. Driving of the pump 15 may be performed at this time so that a uniform discharge capacity is maintained. In this case, when the interruptedstate and the communicated state are variably controlled with a predetermined duty ratio with respect to the valve position of the two-way valve 133, the slope of the relationship between the second brake-fluid pressure PL and the master-cylinderpressure PU can be varied as is indicated by line Y5 or line Z5 in FIG. 5B. Further, execution of duty control of the two-way valve 133 may be started in accordance with the master-cylinder pressure PU or the second brake-fluid pressure PL. In thiscase, the master-cylinder pressure PU and the second brake-fluid pressure PL are in a one-to-one relationship until the master-cylinder pressure PU and the second brake-fluid pressure PL become the predetermined pressure P1 as is indicated by line Z5 orline W5. In a case where the master-cylinder pressure PU and the second brake-fluid pressure PL have become the predetermined pressure P1 or more, the second brake-fluid pressure PL is increased with respect to the master-cylinder pressure PU byvariably controlling the communicated/interrupted state of the two-way valve 133.
Additionally, when execution of communication/interruption control of the two-way valve 133 is started at a uniform duty ration synchronously with the generation of the master-cylinder pressure PU while the pump is being driven at a uniformdischarge capacity, an approximately linear pressure-ratio characteristic having a predetermined slope can be obtained, as is indicated by line Y5 in FIG. 5B.
Up through the description hereinabove, a characteristic in the relationship of the master-cylinder pressure PU and the second brake-fluid pressure PL as indicated by line Y5, line Z5, and line W5 was obtained by variably duty-controlling thetwo-way valve 133 while driving the pump 15 with uniform discharge capacity. However, it is possible also for example to execute the communication/interruption control of the two-way valve 133 at a uniform duty ratio. In this case, to obtain acharacteristic as is indicated in line Y5, line Z5 or line W5, the discharge capacity of the pump 15 is varied. Furthermore, to uniformly or variably control the pump discharge capacity, temperature of the brake fluid or a voltage value or the like forpump drive may be controlled so as to adjust pump capacity.
Next, a second embodiment further adding an antiskid system 30 to a brake control apparatus according to the present invention will be described with reference to FIG. 6. Description will be omitted of structure as well as mode of operation andeffects which are similar to the first embodiment.
The antiskid system 30 (ABS system) is provided with a structure which will be described hereinafter. Firstly, a first pressure-increasing control valve 31 to control increase in pressure of brake fluid to the first wheel cylinder 4 and a secondpressure-increasing control valve 32 to control increase in pressure of brake fluid to the second wheel cylinder 5 are disposed in the second conduit part A2. These first and second pressure-increasing control valves 31 and 32 are made up of a two-wayvalve which controls a communicated/interrupted state. Accordingly, when these two-way valves 31 and 32 have been controlled in a communicated state, brake-fluid pressure due to the master-cylinder pressure PU or the brake fluid discharged from the pump15 can be applied to the several wheel cylinders 4 and 5.
During normal braking wherein antiskid control (ABS control) is not executed, these first and second pressure-increasing control valves 31 and 32 are constantly controlled to a communicated state.
A first pressure-reducing control valve 33 and a second pressure-reducing control valve 34 are respectively disposed in conduits linking the second conduit part A2 between the above-described first and second pressure-increasing control valves 31and 32 and the several wheel cylinders 4 and 5 and a second reservoir hole 26 of a reservoir 20 which will be described later. These first and second pressure-reducing control valves 33 and 34 are caused to be constantly in an interruption state duringnormal braking. Communication/interruption control of these first and second pressure-reducing control valves 33 and 34 is executed in a case where antiskid control has started and the first and second pressure-increasing control valves 31 and 32 havebeen driven in an interrupted state. In the state described earlier, when the first or second pressure-reducing control valve 33 or 34 has been caused to be in an interrupted state, the wheel-cylinder pressure of the corresponding wheel cylinder 4 or 5is maintained. Additionally, when a locking state of a wheel has been detected, the first or second pressure-reducing control valve 33 or 34 is caused to be in a communicated state, and the wheel-cylinder pressure of the corresponding wheel cylinder 4or 5 is reduced. At this time, brake fluid which has been applied to the wheel cylinder 4 or 5 passes through the first or second pressure-reducing control valve 33 or 34 and the second reservoir hole 26 and is stored within a reservoir chamber 27. Asa result, the several wheel-cylinder pressures can be reduced.
Additionally, in a case where restraining a locking tendency of the wheel and increasing the wheel-cylinder pressure are desired, the wheel-cylinder pressure is increased utilizing brake fluid accumulated within the reservoir chamber 27. That isto say, the pump 15 takes in brake fluid from the second reservoir hole 26. The brake fluid discharged from the pump 15 passes through the first or second pressure-increasing control valve 31 or 32, and reaches the wheel cylinder 4 or 5. Thus,brake-fluid pressure is applied to the wheel cylinder 4 or 5.
When brake fluid is accumulated in the reservoir 20 during antiskid control in the way, the pump 15 takes in brake fluid from the second reservoir hole 26 and increases the brake-fluid pressure applied to the several wheel cylinders 4 and 5. Thereservoir 20 is structured so that the flow of brake fluid between the interior of the reservoir 20 and the first conduit part A1 is interrupted in a case where brake fluid is accumulated within this reservoir 20.
Structure of the reservoir 20 will be described hereinafter.
As shown in FIG. 6, the reservoir 20 is connected between the first conduit part A1 and the brake-fluid intake side of the pump 15. This reservoir 20 has a first reservoir hole 25 which is connected to the first conduit part A1 between themaster cylinder 3 and the proportioning control valve 13. The reservoir 20 receives brake fluid from the first conduit part A1 which comes to have pressure equivalent to the master-cylinder pressure PU. A ball valve 21 is disposed further into theinterior of the reservoir 20 than this reservoir hole 25. A rod 23 which has a predetermined stroke to move this ball valve 21 up or down is provided on an underside of this ball valve 21. A piston 24 interlocked with the rod 23 is provided within thereservoir chamber 27. This piston 24 slides downward in a case where brake fluid has flowed from the second reservoir hole 26, accumulating brake fluid within the reservoir chamber 27. Additionally, in a case where brake fluid has been accumulated inthis way, the piston 24 moves downward. The rod 23 also moves downward in accompaniment thereto, and the ball valve 21 contacts a valve seat 22. Accordingly, when the ball valve 21 contact the valve seat by the brake fluid accumulated within thereservoir chamber 27, the communication between the intake side of the pump 15 and the first conduit part A1 is interrupted by the ball valve 21 and the valve seat 22. This ball valve 21 and the valve seat 22 constitute a similar mode of operation evenin a state of ordinary braking prior to execution of antiskid control. That is to say, when the master-cylinder pressure PU has been generated in an ordinary braking state, brake fluid flows through the first conduit part A1 to the reservoir 20. However, when an amount of brake fluid corresponding to the stroke of the rod 23 has accumulated within the reservoir 20, the flow of brake fluid is interrupted by the ball valve 21 and the valve seat 22. Accordingly, the reservoir 20 is not filled withbrake fluid during ordinary braking, and it is possible to cause brake fluid to be contained within the reservoir 20 during pressure-reduction in antiskid control.
As described above, because the ball valve 21 and the rod 23 are formed separately, a containing capacity within the reservoir 20 during pressure-reduction in antiskid control can be gained without the stroke of the rod 23 becoming exceedinglylong.
When brake fluid within a reservoir chamber 27 has been consumed by the intake of the pump 15 during pressure-increasing in antiskid control, the piston 24 moves to the upper side, and the rod 23 pushes the ball valve 21 to the upper side inaccompaniment thereto. Accordingly, the ball valve 21 is separated from the valve seat 22, and the intake side of the pump 15 and the first conduit part A1 are communicated. When communicated in this way, a mode of operation of a pressure-amplifyingdevice 10 is executed; namely, the pump 15 takes in brake fluid from the first conduit part A1 and performs an increase in the wheel-cylinder pressure. Accordingly, there is immediate transfer to pressure-amplifying operation due to thepressure-amplifying device 10 and high braking force can be obtained, even in a case where optimal braking force cannot be obtained solely by the brake-fluid quantity within the reservoir 20, for example when the running road of the vehicle changes froma low-friction (low-.mu.) road to a high-friction (high-.mu.) road.
A spring 28 which compresses the piston 24 to the upper side and generates force which attempts to expel brake fluid within the reservoir chamber 27 is incorporated within the reservoir 20.
When antiskid control has been completed, brake fluid within the reservoir 20 may be returned through the proportioning control valve 13 to the master-cylinder 3 side by the pump 15 so as to empty the interior of the reservoir 20. When this isdone, sufficient brake fluid can be accumulated within the reservoir 20 when subsequent antiskid control is executed and wheel-cylinder pressure is reduced. When spring force of the spring 28 is set to be a predetermined value or more, it becomespossible also to return brake fluid from the first reservoir hole 25 by this spring force.
When the reservoir 20 structured in this way is utilized, the pump 15 for heightening the second brake fluid pressure in the second conduit part A2 and the pump driven when the wheel-cylinder pressure in the antiskid system is increased or thebrake fluid within the reservoir 20 is returned to the master-cylinder 3 side can be used in common.
If a three-port two-way valve which can switch a communication mode between a first mode communicating the intake side of the pump 15 and the reservoir 20 and a second mode communicating the intake side of the pump 15 and the first conduit partA1 is provided in the antiskid system 30, brake fluid accumulated within the reservoir 20 can be controlled to be less than a predetermined quantity. That is to say, when a detector detects the brake fluid quantity more than the predetermined quantityduring ordinary braking or during operation of the pressure-amplifying device 10, the three-port two-way valve is driven to the first mode to reduce the brake fluid quantity within the reservoir 20. As a result, because the brake fluid quantity withinthe reservoir 20 is kept to the predetermined quantity or less, when antiskid control is executed, it is possible to immediately execute pressure-reduction control in antiskid control.
A third embodiment according to the present invention will be described next with reference to FIG. 7 and FIG. 8.
The third embodiment relates to a brake control apparatus including a brake-fluid quantity amplifying device 40 in addition to the pressure-amplifying device 10 described in the first embodiment.
The brake-fluid quantity amplifying device 40 will be described with reference to FIG. 7. The brake-fluid quantity amplifying device 40 is provided with an independent reservoir 41 and an brake-fluid quantity amplifying pump 42 taking in brakefluid from the reservoir 41 and discharge the pressurized brake fluid to a second pressure chamber 47 within a pressure-proportioning cylinder 45.
In the pressure-proportioning cylinder 45, a first pressure chamber 46 into which the master-cylinder pressure PU from the first conduit part A1 is introduced, the second pressure chamber 47, and a third pressure chamber 48 are formed by a piston49 disposed therein. The reservoir 41 is communicated with the second pressure chamber 47. However, when the brake pedal 1 has been depressed and a predetermined pressure has been generated in the master cylinder 3, the communication between thereservoir 41 and the pressure chamber 47 are interrupted by the piston 49 moving leftward in the drawing. Additionally, accompanying this movement of the piston 49, a discharge port of the brake-fluid quantity amplifying pump 42 and the second pressurechamber 47 are communicated. The brake-fluid pressure within the second pressure chamber 47 becomes high pressure. When the depression of the brake pedal 1 is weakened, the master-cylinder pressure PU falls down to a predetermined value, and the piston49 causes the second pressure chamber 47 and the independent reservoir 41 to communicate as shown in FIG. 7, the brake-fluid pressure of the second pressure chamber 47 is released to the reservoir 41 side. At this time, the discharge port of thebrake-fluid quantity amplifying pump 42 is interrupted by the piston 49 moving rightward in the drawing.
The third pressure chamber 48 and the second pressure chamber 47 are communicated via a brake-fluid quantity amplifying proportioning control valve 43. This brake-fluid quantity amplifying proportioning control valve 43 attenuates thebrake-fluid pressure from the second pressure chamber 47 with a predetermined ratio and conveys the attenuated brake-fluid pressure to the third pressure chamber 48.
The relationship between the brake-fluid pressure introduced in the third pressure chamber 48 through the brake-fluid quantity amplifying proportioning control valve 43 and the brake-fluid pressure within the second pressure chamber 47 when thebrake-fluid pressure of the second pressure chamber 47 has been caused to be high pressure by the brake-fluid quantity amplifying pump 42 is determined by the attenuation ratio established in the brake-fluid quantity amplifying proportioning controlvalve 43.
The piston 49 is moved laterally by the relationship between the master-cylinder pressure PU and the brake-fluid pressure in the third pressure chamber 48. When the brake fluid pressure in the third pressure chamber 48 is larger than themaster-cylinder pressure PU, the second pressure chamber 47 communicates with the reservoir 41 and the communication of brake-fluid quantity amplifying pump 42 and the second pressure chamber 47 is prohibited. As a result, the brake fluid pressure inthe second pressure chamber 47 is reduced. The brake fluid pressure in the third pressure chamber 48 is also reduced in response to decrease of the brake fluid pressure in the second pressure chamber 47. However, the brake fluid pressure in the thirdpressure chamber 48 is lower than the brake fluid pressure in the second pressure chamber 47 by a value corresponding to an attenuation ratio of the brake-fluid quantity amplifying proportioning control valve 43. When the brake fluid pressure in thethird pressure chamber 48 reduces below the master-cylinder pressure PU, the piston 49 moves leftward in the drawing. As a result, the brake-fluid quantity amplifying pump 42 is communicated with the second pressure chamber 47 and the communicationbetween the second pressure chamber 47 and the reservoir 41 is interrupted. Accordingly, the brake-fluid pressure in the second pressure chamber 47 is increased by the pressurized brake fluid discharged from the brake-fluid quantity amplifying pump 42. In this way, the brake-fluid pressure in the second pressure chamber is kept to the pressure higher than the master cylinder pressure PU by the value corresponding to the attenuation ratio of the brake-fluid quantity amplifying proportioning controlvalve 43.
Communication or interruption of the brake-fluid within the second pressure chamber 47 to the second conduit part A2 is controlled by a brake-fluid quantity amplifying control valve 44. This brake-fluid quantity amplifying control valve 44 isnormally caused to be in an interrupted state, but is controlled to a communicated state according to vehicle behavior such as a slippage state of a wheel. When the brake-fluid quantity amplifying control valve 44 has been caused to be in a communicatedstate, high-pressure brake fluid flows through the brake-fluid quantity amplifying control valve 44 to the several wheel cylinders 4 and 5. Further, the brake-fluid quantity amplifying control valve 44 is not exclusively limited to being controlledaccording to the vehicle behavior, but may be controlled in accordance with a state of the brake pedal 1. For example, the brake-fluid quantity amplifying control valve 44 is controlled to a communicated state when the brake pedal 1 has been depressedand a predetermined period of time has elapsed.
In the brake control apparatus having the brake-fluid quantity amplifying device 40, brake-fluid pressure even higher than the second brake-fluid pressure PL of the second conduit part A2 increased by the pressure-amplifying device 10 can berealized. Additionally, brake-fluid quantity comes to be amplified with respect to the brake fluid in the second conduit part A2 as a result that brake fluid is supplied to the second conduit part A2 from the independent reservoir 41. When theoperation of the brake-fluid quantity amplifying device 40 is started subsequently to termination of operation of, for example, the pressure-amplifying device 10, still greater braking force can be ensured by the brake-fluid quantity amplifying device 40while maintaining a lowered state of depression force due to the pressure-amplifying device 10 and causing only a light burden to remain with the driver. At this time, suitable reaction force can be caused to remain with pedal feel without furtheralleviation of the reaction force being performed, due to the operation of the pressure-amplifying device 10 being terminated. Additionally, when switched from operation of the pressure-amplifying device 10 to operation of the brake-fluid quantityamplifying device 40, reduction of the brake-fluid quantity of the first conduit part A1, i.e., reduction of the brake-fluid pressure within the first conduit part A1, by the pressure-amplifying device 10 is terminated. The pressure of the secondconduit part A2 is increased due to brake-fluid quantity amplification, and so it becomes possible to prevent excessive lengthening of the pedal stroke while ensuring braking force.
Amplification of the brake-fluid quantity with respect to the second conduit part A2 by the brake-fluid quantity amplifying device 40 and movement and pressure-increasing of brake fluid from the first conduit part A1 to the second conduit part A2by the pressure-amplifying device 10 may be alternately switched and controlled or simultaneously executed. In this case, alleviation of the reaction force and amplification of the pressure applied to the wheel cylinders 4 and 5 by thepressure-amplifying device 10 can be realized. At the same time, it is possible to prevent the reaction force from the brake pedal 1 to an extremely low value and impart an appropriate reaction force to the driver by the pressure-amplifying device 10.
A modification of the above-described third embodiment will be described next with reference to FIG. 8.
FIG. 8 indicates a brake-fluid quantity amplifying device 50 which can be substituted for the brake-fluid quantity amplifying device 40 in FIG. 7.
This brake-fluid quantity amplifying device 50, similarly to the foregoing third embodiment, is provided with an independent reservoir 41 and a brake-fluid quantity amplifying pump 42 which can taken in brake fluid from the reservoir 41 anddischarge the brake fluid under high pressure. The discharge line of the brake-fluid quantity amplifying pump 42 is connected to the second conduit part A2 via the brake-fluid quantity amplifying control valve 44. A brake-fluid quantity amplifyingproportioning control valve 43 which attenuates the brake-fluid pressure with a predetermined attenuation ratio when high-pressure brake fluid from the brake-fluid quantity amplifying pump 42 has passed is connected to a conduit extending from theconduit between the discharge side of the brake-fluid quantity amplifying pump 42 and the brake-fluid quantity amplifying control valve 44. A check valve 55 is disposed in a conduit connecting the brake-fluid quantity amplifying proportioning controlvalve 43 and the first conduit part A1. This check valve 55 acts so that the master-cylinder pressure PU from the first conduit part A1 side and the pressure of the brake fluid existing between the brake-fluid quantity amplifying proportioning controlvalve 43 and the check valve 55 become substantially identical. That is to say, the check valve 50 acts so that the master-cylinder pressure PU and the brake-fluid pressure attenuated by the brake-fluid quantity amplifying proportioning control valve 43in brake fluid discharged by the brake-fluid quantity amplifying pump 42 become substantially identical in pressure. In more detail, the check valve 50 compares the master-cylinder pressure PU and the brake-fluid pressure attenuated by the brake-fluidquantity amplifying proportioning control valve 43. When the brake-fluid pressure between the brake-fluid quantity amplifying proportioning control valve 43 and the check valve 55 has become higher than the master-cylinder pressure PU, the brake-fluidpressure in a fluid chamber 51 in the check valve 55 is reduced based on the fact that the brake fluid returns to the reservoir 41 via a hole 52. As a result, brake-fluid pressure equivalent to the master-cylinder pressure PU is obtained in the fluidchamber 51. When the brake-fluid pressure in the fluid chamber becomes below the master-cylinder pressure PU, the brake fluid pressurized by the brake-fluid quantity amplifying pump 42 is introduced into the fluid chamber via the brake-fluid quantityamplifying proportioning control valve 43. As a result, the brake-fluid pressure of the conduit between the brake-fluid quantity amplifying control valve 44 and the brake-fluid quantity amplifying pump 42, which is heightened by the pressurized brakefluid discharged from the brake-fluid quantity amplifying pump 42 is increased or reduced to a pressure value of a predetermined ratio with respect to the master-cylinder pressure PU. That is to say, in a case where the master-cylinder pressure PU isnot less than the split-point pressure of the brake-fluid quantity amplifying proportioning control valve 43, the brake-fluid pressure of the conduit between the brake-fluid quantity amplifying control valve 44 between the brake-fluid quantity amplifyingpump 42 is increased at a reciprocal multiple of the attenuation ratio established in the brake-fluid quantity amplifying proportioning control valve 42 with respect to the master-cylinder pressure PU. Accordingly, when the established value of theattenuation ratio established in the brake-fluid quantity amplifying proportioning control valve 42 is uniform, the brake-fluid pressure of the conduit between the brake-fluid quantity amplifying control valve 44 between the brake-fluid quantityamplifying pump 42 is increased or reduced, accompanying the increase or reduction in the master-cylinder pressure PU, in inverse proportion to the attenuation ratio established in the brake-fluid quantity amplifying control valve 44.
In this way, brake fluid cause to be at a high brake-fluid pressure in response to the master-cylinder pressure PU flows to the second conduit part A2 due to the brake-fluid quantity amplifying control valve 44 being communicated. As a result,the brake-fluid quantity of the second conduit part A2 is amplified. By performing amplification of the brake-fluid quantity in this way, effects similar to the third embodiment described earlier can be obtained.
Furthermore, the check valve 55 may act so as to cause the brake-fluid pressure in the conduit between the brake-fluid quantity amplifying proportioning control valve 43 and the check valve 55 not to be identical with the master-cylinder pressurePU but rather to be pressure having a predetermined ratio with respect to the master-cylinder pressure PU.
Additionally, it is possible to omit the brake-fluid quantity amplifying control valve 44; In this case, pressure-amplification by the pressure-amplifying device 10 with respect to the second conduit part A2 and amplification of the brake-fluidquantity by the brake-fluid quantity amplifying device 50 are executed simultaneously in accordance with the generation of the master-cylinder pressure PU. Accordingly, the reaction-force alleviation and increase in pressure due to the movement of brakefluid from the first conduit part A1 to the second conduit part A2 executed by the pressure-amplifying device 10, and an increase in pressure and prevention of an excessive increase in pedal stroke due to the increase in the brake-fluid quantity withrespect to second conduit part A2 by the brake-fluid quantity amplifying device 50 can both be realized.
The restrictor 132 making up the pressure-amplifying device 10 in FIG. 7 may be replaced with the proportioning control valve 13 described in the first embodiment. In this case, the split-point pressure in this proportioning control valve 13 andthe split-point pressure in the brake-fluid quantity amplifying proportioning control valve 43 may be established at differing values. When, for example, the split-point pressure in the brake-fluid quantity amplifying proportioning control valve 43 isestablished to be greater than the split-point pressure in the proportioning control valve 13, the brake-fluid quantity is amplified only in a case where the second brake-fluid pressure PL in the second conduit part A2 has become greater than thesplit-point pressure established in the proportioning control valve 13 and moreover has become greater than the split-point pressure established in the brake-fluid quantity amplifying proportioning control valve 43.
A fourth embodiment will be described next with reference to FIG. 10. For structure exhibiting a mode of operation and effects similarly to the embodiments described hereinabove, symbols similar to the foregoing will be attached and descriptionthereof will be omitted.
A characteristic point of the fourth embodiment exists in that the proportioning control valve 13 as the holding device and the pump 15 as the brake-fluid moving device are incorporated within the wheel cylinders 4 and 5 to generate braking forceat the wheels. That is to say, the proportioning control valve 13 and the pump 15 are disposed within components of the wheel cylinders 4 and 5. Moreover, a conduit communicating between the proportioning control valve 13 and pump 15 and a wheel piston63 to actually generate wheel braking force is also disposed within the components of the wheel cylinders 4 and 5.
When the wheel piston 63 receives brake-fluid pressure and is moved rightward in the drawing, a pad 61 is compressed against a disc rotor 60 and braking force is generated at the wheel. The disc rotor 60 rotates integrally with the wheel, andthe wheel is braked by friction between the disc rotor 60 and the pad 61.
The pump 15 in this embodiment receives drive energy from the disc rotor 60 rotating together with the wheel. That is to say, a transmission member 62 interconnecting the interval between the pump 15 and the disc rotor 60 and transmitting therotational energy of the disc rotor 60 to the pump 15, and a clutch 65 disposed in this transmission member 62 to control an interconnected state between the pump 15 and the disc rotor 62 are provided.
The transmission member 62 may be disposed to be eccentric by a predetermined quantity from the center of a wheel axle 64, so as to generate piston motion or scroll motion or the like in the pump 15. In this embodiment, the clutch 65 isstructured solely on the rear-wheel side, and is not provided on the front-wheel side. As a result, the front-wheel side is in a state of constantly being driven by the pump 15 while the wheels are rotating. However, when master-cylinder pressure hasnot been generated, the proportioning control valve 13 does not exert pressure-holding action. Therefore, brake fluid merely circulates along the conduit, and the pad 61 is not pushed toward the disc rotor 60. Moreover, because hydraulic pulsationconstantly acts upon the wheel piston 63 due to the brake fluid circulating in this way, clearance between the wheel piston 63 and the pad 61 can be maintained at a minimum distance, and initial response at the time of brake-pedal depression can beenhanced. That is to say, because force is constantly applied to the wheel piston 63 by the hydraulic pulsation, there is no movement of the wheel piston 63 leftward in the drawing and no enlargement of clearance due to body vibration or the like. Additionally, when the pump 15 is constantly driven on the front-wheel side, a constant pressure-amplifying action is exerted at a time that master-cylinder pressure not less than the split-point pressure of the proportioning control valve 13 has beengenerated in the master cylinder 3 when the brake pedal 1 has been depressed by the driver. Furthermore, the rotational speed and discharge pressure (discharge quantity per unit time) of the pump 15 also change in accordance with wheel rotational speed. That is to say, the discharge pressure of the pump 15 becomes small in a case where wheel rotational speed is low, and the discharge pressure of the pump 15 becomes large in a case where wheel rotational speed is high. Even when the master-cylinderpressure PU is uniform, a large pressure-amplifying action can be exhibited in a case where wheel rotational speed is high, and only a small pressure-amplifying action is exhibited in a case where wheel rotational speed is low. As a result, so-calledjerky braking can be prevented in a case where body speed is low. Further, pressure-increase gain of the brake-fluid pressure applied to the wheel piston 63 can be made to be large and short-distance braking can be realized in a case where body speed ishigh.
Because a clutch 65 is employed on the rear-wheel side, the brake control apparatus may be such that the clutch 65 is connected and pressure-amplifying action is realized after a predetermined time has elapsed subsequently to, for example,brake-pedal depression.
An electrical type clutch mechanism may be utilized in this clutch 65, or a mechanical type clutch mechanism may be also utilized. When, for example, an electrical type clutch mechanism has been actuated, a brake-switch signal (not illustrated)may be received and the clutch connected; when a mechanical type clutch mechanism has been employed, the clutch may be connected when the master-cylinder pressure becomes a predetermined pressure.
In the fourth embodiment, rotational energy of the wheel can be recovered with favorable efficiency and utilized to drive the pump. That is, a role can be played in regenerative braking.
When the fourth embodiment is applied in an electric vehicle, great energy can be obtained in comparison with regenerative braking by a retarder of known art and in particular braking-force insufficiency during rapid braking can be avoided.
In the fourth embodiment, the pressure-increasing control valves 31 and 32 and the pressure-reducing control valves 33 and 34 realizing antiskid-control action are disposed between the master cylinder 3 and the wheel cylinders 4 and 5 as shown inFIG. 10. Further, an ABS pump 35 to discharge brake fluid accumulated in an ABS reservoir 36 which accumulates brake fluid corresponding to the amount of reduction in wheel-cylinder pressure during antiskid control is provided. Pressure-increasing andpressure-reducing control is executed within a range of lower pressure than the brake-fluid pressure applied to the wheel piston 63 in the interval from the master cylinder 3 to the proportioning control valve 13. Therefore, load applied to the severalcontrol valves and the like is alleviated.
Brake piping and an ABS actuator block mounted on a vehicle will be described next as a fifth embodiment with reference to FIG. 11. For structure exhibiting a mode of operation and effects similarly to the embodiments described. hereinabove,symbols similar to the foregoing will be attached and description thereof will be omitted.
A first conduit A and a second conduit B are illustrated in FIG. 11; diagonal piping is employed wherein the wheel cylinder 4 of the front-right wheel FR and the wheel cylinder 5 of the rear-left wheel RL are connected to the first conduit A andthe wheel cylinder of the front-left wheel FL and the wheel cylinder of the rear-right wheel RR are connected to the second conduit B.
In an ABS actuator 30A, a total of four pressure-increasing control valves and a total of four pressure-reducing control valves respectively disposed in the first conduit A and the second conduit B, a total of two reservoirs, a total of twopumps, and a motor to drive these pumps are components in a single block.
Proportioning control valves 13 disposed respectively in the first conduit A and the second conduit B are each structured by an integrated proportioning control-valve block 13A.
When the ABS actuator 30A and the integrated proportioning control-valve block 13A are formed into discrete components connected by the first and second conduits A and B, an ABS actuator 30A having little need to change its specifications foreach vehicle type can be used in common for several vehicle types. Instead, the proportioning control valves 13 for which there is great need to vary establishment of split points and so on for each of several vehicle types can alone be caused to havethe specification suitable for each vehicle type. When the ABS actuator 30A common for several vehicle types can be employed, overall product cost can be reduced.
To describe in detail the structure of the integrated proportioning control-valve block 13A, master-cylinder pressure PU generated in the master cylinder 3 during ordinary braking is conveyed to second conduit parts A2 and B2 through firstconduit parts A1 and B1 and valve seals 135, with substantially no pressure attenuation. The conveyed brake-fluid pressure is applied to the several wheel cylinders 4 and 5. Thereafter, when brake fluid is taken in from the first conduit parts A1 andB1 and discharged to the second conduit parts A2 and B2 by the pumps, this brake-fluid pressure of the second conduit parts A2 and B2 becomes second brake-fluid pressure which is higher than the master-cylinder pressure PU.
Accordingly, a proportioning control-valve piston 136 is constantly compressed upwardly by a coil spring 137 until the second brake-fluid pressure becomes a split-point pressure or more and during ordinary braking. Consequently, a clearance isopened between the valve seal 135 and the proportioning control-valve piston 136. The first conduit parts A1 and B1 and the second conduit parts A2 and B2 assume a state of communication. When the brake-fluid pressure in the second conduit parts A2 andB2 reaches the split-point pressure due to pump discharge, the force applied to the proportioning control-valve piston 136 becomes larger than the spring force of the coil spring 137. The proportioning control-valve piston 136 is pressed to an airchamber 138 side (lower in the drawing). The valve seal 135 and a shoulder portion of the proportioning control-valve piston 136 make contact due to this action, interrupting the communication. Furthermore, when the brake-fluid pressure in the secondconduit parts A2 and B2 becomes higher than the split-point pressure, force to press the proportioning control-valve piston 136 upwardly is exerted. The master-cylinder pressure is exerted as force to press the proportioning control-valve piston 136downward. Therefore, action of the proportioning control-valve piston 136 is such that these two forces are held in balance. In this way, the proportioning control-valve piston 136 constantly repeats minute oscillation and reduces pressure conveyedfrom the second conduit parts A2 and B2 to the first conduit parts A1 and B1 by a defined pressure in a case where the brake-fluid pressure of the second conduit parts A2 and B21 is displaced at a higher pressure than the split-point pressure. Thepressure of the second conduit parts A2 and B2 is maintained at a higher level by the defined pressure than the brake-fluid pressure of the first conduit parts A1 and B1. Because the brake-fluid pressure of the second conduit parts A2 and B2 acts uponan annular cross-sectional area B-A (where B>A) which is a valve-seal diameter cross-sectional area B minus a cross-sectional area A of the proportioning control-valve piston 136. The master-cylinder pressure PU acts upon the valve-seal diametercross-sectional area B. As a result, the brake-fluid pressure of the second conduit parts A2 and B2 maintains equilibrium in the proportioning valves 13 at a high fluid pressure compared with the master-cylinder pressure PU. This fluid-pressureequilibrium ratio is, in other words, the attenuation ratio of the brake-fluid pressure in the second conduit parts A2 and B2. This is determined by the ratio (B/A) of the two pressure-receiving surface areas A and B. When this ratio (B/A) is large theattenuation ratio is increased, and the pressure-increasing gradient of the brake-fluid pressure in the second conduit parts A2 and B2 becomes greater. Accordingly, in a case where the present embodiment has been employed, for example, in front-rearpiping, when the ratio (B/A) of the pressure-receiving surface areas A and B of the proportioning control valve 13 on the rear-wheel side is established at a low value and the ratio (B/A) of the pressure-receiving surface areas A and B of theproportioning control valve 13 on the front-wheel side is established at a high value, large brake-fluid pressure is applied to the wheel cylinders on the front-wheel side and brake-fluid pressure lower than for the front-wheel side is applied to thewheel cylinders on the rear-wheel side when pumps having the same discharge capacity are driven with respect to the front and rear wheels. As a result, braking-force distribution for the front and rear wheels can be realized while applying higherpressure than the master-cylinder pressure to the front and rear wheel cylinders. Further, 139 is a cap.
A sixth embodiment will be described next with reference to FIG. 12. For structure exhibiting a mode of operation and effects similarly to the embodiments described hereinabove, symbols similar to the foregoing will be attached and descriptionthereof will be omitted.
As shown in FIG. 12, a first conduit A and a second conduit B are respectively provided with pumps 15A and 15B to taken in brake fluid from the master cylinder 3 side and discharge the brake fluid toward the several wheel cylinders 4 and 5. These pumps 15A and 15B are respectively provided with conduits A10 and B10 in parallel, and are formed so that pump discharge is refluxable.
The flowchart shown in FIG. 13 indicates a condition for starting to drive the pumps 15A and 15B. Firstly, in step S1, initialization for several flags and the like is performed. In step S2, input from a brake switch (not illustrated) isreceived. This brake switch assumes an "on" state when the brake pedal 1 has been depressed by the driver, producing a vehicle-braking state. In step S3, it is determined whether the brake switch is ON. In a case where the determination isaffirmative, the process advances to step S4. A motor (not illustrated) to drive the pumps 15A and 15B is electrified, and pump intake and discharge operation is executed. The process advances to step S5 and it is determined whether a predeterminedtime has elapsed since starting to electrify the motor. In a case where the determination is affirmative, the process advances to step S6; in a case where the determination is negative, the process returns to step 3. In step S6, the electrification ofthe motor is switched off. Furthermore, in step S3, the process advances to step S6 in a case where the determination is negative.
Mode of operation and effects will be described hereinafter with reference to FIG. 14. Change in wheel-cylinder pressure is illustrated in a case where the brake switch is in an "on" state, i.e., where a vehicle-braking state is obtained. Thesolid line in the drawing represents change in wheel-cylinder pressure in a case where there is control by the present embodiment wherein the motor is electrified, the dotted line represents change in wheel-cylinder pressure in a case where there is nocontrol by this embodiment, and the double-dotted broken line represents change in wheel-cylinder pressure in a case where fluid resistance of the brake fluid is assumed to be substantially nonexistent. As is understood from FIG. 14, in the presentembodiment the speed of movement of the brake fluid can be assisted by pump drive and reflux of the brake fluid. Fluid resistance can be alleviated, and so response in increasing wheel-cylinder pressure can be enhanced.
As shown in FIG. 15, pump drive control may be executed in response to change in pedal stroke. That is to say, in step S11, initialization is performed, and in step S12, pedal stroke PS is detected by a stroke sensor (not illustrated). In stepS13, it is determined whether present pedal-stroke detected value PS (n) is greater than previous pedal-stroke detected value PS (n-1). When determined in the affirmative, the motor is electrified in step S14. In a case where the determination isnegative, the process advances to step S15. In step S15, it is determined whether a predetermined time has elapsed since electrification of the motor. In a case where the determination is affirmative, the process advances to step S16, and motorelectrification is stopped. In a case where the determination is negative, the process returns to step S12.
In this way, a similar effect can be obtained even when brake-fluid movement speed is assisted by the pump when there exists change in pedal stroke. Moreover, because play is present in an ordinary brake pedal, the pump can be driven in theinterval of play in the pedal if the pump drive is stated in response to change in brake-pedal stroke. As a result, brake-fluid flows within the first conduit A while master-cylinder pressure PU is actually being generated. Accordingly, it is possibleto respond sufficiently even during the initial period of brake-pedal depression. Furthermore, master-cylinder pressure, depression force, or the like may be detected as a value corresponding to the stroke of the brake pedal, to control pump drive.
A modification of the embodiments hereinabove will be described hereinafter.
In, for example, the first embodiment or the like, the pressure-amplifying device 10 was made up of the pump 15 and the holding device 13. However, the pressure-amplifying device 10 is not exclusively restricted thereto, and may utilize a simplestructure directly connecting the pump 15 in the first conduit A, as shown in FIG. 9. In this case, movement of brake fluid may be realized by, for example, disposing the pump 15 so as to be buried within the first conduit A and driving the pump 15 inthe normal direction in accordance with the operating state of the brake pedal 1, in order to take in the brake fluid of the first conduit part A1 and discharge the brake fluid to the second conduit part A2. In a case where weakening of the pedaldepression force by the driver has been detected from the brake-pedal state, the pump 15 may be driven in reverse direction so as to reduce the brake-fluid pressure applied to the wheel cylinders to a normal state. Furthermore, it is preferred that aholding device such as to cause the pressure in the second conduit part A2 to be at least the master-cylinder pressure PU or more be provided in the pump 15 so that at least the master-cylinder pressure PU is applied to the wheel cylinders even in a casewhere failure of the pump 15 may have occurred.
In the embodiments hereinabove, pressure amplification of the second conduit part A2 by the pressure-amplifying device 1, and amplification of brake-fluid quantity with respect to the second conduit part A2 by the brake-fluid quantity amplifyingdevice 40 were performed with respect to both the front-right wheel FR and the rear-left wheel RL. However, pressure amplification by the pressure-amplifying device 10 or amplification of brake-fluid quantity with respect to the second conduit part A2by the brake-fluid quantity amplifying device 40 may be performed only at the front-right and front-left wheels. There may be cases wherein assurance of braking force in the rear-right and rear-left wheels cannot be expected due to load movementoccurring during vehicle braking. When great load movement occurs, it even arises possibility that the rear wheels become prone to slippage when large braking force is applied to the rear wheels. In such a case, efficient braking force can be gained byperforming pressure amplification only at the front-right and front-left wheels.
The brake-fluid quantity amplifying pump 42 was employed as the brake-fluid quantity amplifying device 40 described with reference to FIG. 7 and FIG. 8, to take in brake fluid from the reservoir 41 and discharge high-pressure brake fluid. However, it is also possible to replace this brake-fluid quantity amplifying pump 42 and reservoir 41 with a fluid-collecting chamber to collect a predetermined quantity of brake fluid at high pressure. The brake-fluid quantity of the second conduitpart A2 may be amplified utilizing the high-pressure brake fluid from this fluid-collecting chamber.
In the embodiments hereinabove, the generation of brake-fluid pressure by the brake-fluid pressure-generating device was realized by the master-cylinder pressure PU being generated in the master cylinder 3 due to the driver operating the brakepedal 1. However, the present invention may be applied in an automatic brake apparatus which actuates a brake when, for example, distance between vehicles has become a predetermined distance or less, irrespectively of brake-pedal depression by a driver. In this case, a pump or the like for automatic-brake use may be provided as the brake-fluid pressure-generating device in substitution for the brake pedal, master cylinder, and soon. Also, load for generating the first brake-fluid pressure in the pumpand the like making up the brake-fluid pressure-generating device can be alleviated when the pressure-amplifying device 10 is provided.
Because the second brake-fluid pressure can be increased by the pressure-amplifying device 10 according to the forgoing embodiments, it is possible to reduce the capacity of the booster 2 provided in the foregoing embodiments and make the booster2 compact, or even to eliminate the booster 2. That is to say, the load on pedal depression force by the driver can be sufficiently lessened and high braking force can be ensured even when there is no pressure-increasing action on the master-cylinderpressure PU by the booster 2.
Furthermore, in the above-described embodiments this invention was applied in a front-wheel drive vehicle with diagonal piping. However, the present invention can be carried out without restriction to a particular drive format or piping system,and is applicable even in a vehicle provided with, for example, T-T piping of connecting front-right wheel cylinder and front-left wheel cylinder and of connecting rear-right wheel cylinder and rear-left wheel cylinder.
A seventh embodiment will be described with reference to FIG. 16.
This embodiment combines an antiskid control system with the basic structure of a brake control apparatus; herein will be described an example wherein a brake control apparatus for a vehicle according to the present invention is applied in avehicle of diagonal piping provided with respective conduits of connecting a front-right wheel cylinder and a rear-left wheel cylinder and of connecting a front-left wheel cylinder and a rear-right wheel cylinder in a front-wheel drive, four-wheeled car.
Firstly, basic structure of the brake control apparatus will be described with reference to the model diagram indicated in FIG. 16. For structure exhibiting a mode of operation and effects similarly to the embodiments described hereinabove,symbols similar to the foregoing will be attached and description thereof will be provided briefly.
In FIG. 16, a brake pedal 1 depressed by a driver when applying braking force to the vehicle is connected to a booster 2, and depression force applied to the pedal 1 and pedal stroke are conveyed to this booster 2.
A master cylinder 3 imparts brake-fluid pressure boosted by the booster 2 to the entirety of a brake conduit. The master cylinder 3 is provided with an independent master reservoir 3a to supply brake fluid to within the master cylinder 3 or toaccumulate excess brake fluid from the master cylinder 3.
The master-cylinder pressure PU generated in the master cylinder 3 is conveyed to brake fluid within a first conduit A linking the master cylinder 3 and a first wheel cylinder (W/C) 4 disposed in the front-right wheel FR to impart braking forceto this wheel FR, and the master cylinder 3 and a second wheel cylinder 5 disposed in the rear-left wheel RL to impart braking force to this wheel RL. The master-cylinder pressure PU is similarly conveyed also to a second conduit B linking respectivewheel cylinders disposed in the front-left wheel and the rear-right wheel to the master cylinder 3.
The first conduit A is made up of two parts separated by a pressure-amplifying device 10 disposed in this first conduit A. That is to say, the first conduit A has a first conduit part A1 to receive the master-cylinder pressure PU in the intervalfrom the master cylinder 3 to the pressure-amplifying device 10 and a second conduit part A2 in the interval from the pressure-amplifying device 10 to the first wheel cylinder 4. Furthermore, the foregoing first conduit part A1 is provided with a firstbranching conduit part A1a extending from the master cylinder 3 via a reservoir 20 to a pump 15, and a second branching conduit part A1b extending from the master cylinder 3 to the second wheel cylinder 5.
The pressure-amplifying device 10 moves brake fluid of the first conduit part A1 to the second conduit part A2 and holds the pressure at the second conduit part A2 at second brake-fluid pressure PL when the brake pedal 1 is depressed and themaster-cylinder pressure PU is generated within the first conduit A. According to the seventh embodiment, this pressure-amplifying device 10 is made up of a proportioning control valve (PV) 13 and a pump 15.
The pump 15 is connected to the first conduit A in series with the proportioning control valve 13, and takes in brake fluid from the first branching conduit part A1a and discharges brake fluid to the second conduit part A2 during generation ofthe master-cylinder pressure PU.
In a case where brake fluid has been moved from the first branching conduit part A1 to the second conduit part A2 by the pump 15 and the brake-fluid pressure of the second conduit part A2 has become the second brake-fluid pressure PL which isgreater than the master-cylinder pressure PU, the proportioning control valve 13 acts to maintain this differential pressure (PL-PU).
In this way, the pressure-amplifying device 10 provided with the pump 15 and the proportioning control valve 13 moves the brake fluid of the first conduit part A1 which generates the master-cylinder pressure PU accompanying depression of thebrake pedal 1 to the second conduit part A2. As a result, the brake-fluid pressure within the first conduit location A1, i.e., the master-cylinder pressure is reduced, and simultaneously thereto, the differential pressure of the second brake-fluidpressure PL amplified within the second conduit part A2 and the master-cylinder pressure PU is maintained. In this way, the pressure-amplifying device 10 performs pressure amplification.
Consequently, the second brake-fluid pressure PL which is greater than the master-cylinder pressure PU is applied via the second conduit part A2 to the first wheel cylinder 4, and so high braking force is imparted to the front-wheel side (i.e.,to the front-right wheel FR). Meanwhile, the master-cylinder pressure PU which is lower than the second brake-fluid pressure PL is applied via the second branching conduit part A1b to the second wheel cylinder 5. Accordingly, braking force lower thanon the front-wheel side is imparted to the rear-wheel side (i.e., to the rear-left wheel RL).
Antiskid control and pressure-amplifying control (i.e., control by the pressure-amplifying device 10) which causes brake fluid to be moved from the master cylinder 3 side to the side of the wheel cylinder 4 and thereby heightens braking force areperformed by an electronic control unit (ECU) not illustrated. This ECU is structured as a microcomputer provided with a CPU, a ROM, a RAM, an input/output portion, a bus line, and the like of known art.
According to the seventh embodiment, the first conduit part A1 of the low-pressure side and the second conduit part A2 of the high-pressure side are structured by disposing the pressure-amplifying device 10 in the first conduit A and connectingthe proportioning control valve 13 in a reverse direction. Further, the first conduit part A1 is made up of the first branching conduit part A1a extending from the master cylinder 3 via the reservoir 20 to the pump 15, and the second branching conduitpart A1b extending from the master cylinder 3 to the second wheel cylinder 5. Therefore, the high-pressure second brake-fluid pressure PL is applied to the first wheel cylinder 4 and the master-cylinder pressure PU lower than the second brake-fluidpressure PL is applied to the second wheel cylinder 5.
Consequently, because the second brake-fluid pressure PL which is higher in pressure than the master-cylinder pressure PU is applied to the first wheel cylinder 4, high pressure is imparted to the front-wheel side (i.e., to the front-right wheelFR) and high braking force can be demonstrated. Meanwhile, because the master-cylinder pressure PU is applied to the rear-wheel side (i.e., to the rear-left wheel RL), susceptibility to the occurrence of locking is reduced.
This state is indicated in FIGS. 17A and 17B; in an example wherein a pressure-amplifying device according to the present embodiment is absent and a proportioning control valve is connected in the normal direction with respect to the rear-leftwheel RL, the state of pressure of the front-right wheel FR and the rear-left wheel RL is such that both are suppressed to an equal to or lower level than the wheel-cylinder pressure PU (W/C pressure), as shown in FIG. 17A. However, according to theseventh embodiment, the state of pressure of the front-right wheel FR and the rear-left wheel RL is such that both are established at higher levels compared with the prior art, as shown in FIGS. 17B.
That is to say, due to structure such as this, ideal braking-force distribution at the front and rear wheels is obtained. That is to say, the brake-fluid pressure applied to the wheel cylinder 4 on the front-wheel side is caused to be greaterthan the brake-fluid pressure applied to the wheel cylinder 5 on the rear-wheel side and brake-fluid pressure can be established at a high value overall. Therefore, braking force for the vehicle overall can be enhanced while demonstrating an effect oflessening depression force.
Additionally, because brake-fluid pressure higher than the master-cylinder pressure PU is applied to the front-wheel side and master-cylinder pressure PU is applied as-is to the rear-wheel side, there exists an effect wherein the wheel-cylinderpressure can be increased with maximum efficiency without causing any loss in the master-cylinder pressure PU.
Furthermore, because an antiskid control system 30 is provided in this embodiment, there exists an advantage in that locking of the wheels does not occur even when the brake-fluid pressure applied to the wheel cylinder 4 on the front-wheel sideis caused to become greater than the brake-fluid pressure PU applied to the wheel cylinder 5 on the rear-wheel side. As a result, the brake-fluid pressure is established at a high level overall.
In this embodiment, an example which does not dispose a proportioning control valve in a conduit connecting to the second wheel cylinder 5 was described. However, a proportioning control valve may be connected in the normal direction as in theprior art. In this case, the difference between the brake-fluid pressure of the second wheel cylinder 5 and the brake-fluid pressure of the first wheel cylinder 4 can be caused to be still larger.
It is to be noted that the conduit A1a connecting the master cylinder 3 side and the reservoir 20 may be deleted and the reservoir 20 may be structured as a normal reservoir which is used in an antiskid system as shown in FIG. 59. In thismodification, to establish wheel-cylinder pressure higher than master-cylinder pressure, ECU executes control as described below.
Firstly, well-known antiskid control is executed with respect to the front and rear wheels FR and RL. In this antiskid control, when the locking tendency (slip ratio) of the rear wheel RL becomes large, the pressure-increasing control valve 32is interrupted and the pressure-decreasing control valve 34 is communicated to reduce the brake-fluid pressure applied to the wheel cylinder 5. At that time, the pump 15 takes in the brake fluid discharged from the wheel cylinder 5 and sends out it tothe second conduit part A2. Therefore, due to the pressure-holding function of the proportional control valve 13, the brake fluid pressure applied to the wheel cylinder 4 of the front wheel FR is increased to a brake-fluid pressure higher than themaster-cylinder pressure.
In this way, even if the conduit A1a is deleted, the wheel braking-force exhibited by the front wheel FR can be increased in accompaniment to antiskid control.
When the above-described control is executed, it is preferable that the braking force is distributed to the front wheel FR and the rear wheel RL so that the rear wheel RL locks prior to the front wheel FR in the master-cylinder pressurecorresponding to urgent braking. As a result, when antiskid control is executed with respect to the rear wheel RL and the brake fluid pressure of the wheel cylinder 5 is reduced during urgent braking, the brake-fluid pressure in the wheel cylinder 4 ofthe front wheel FR is increased to a pressure higher than the master-cylinder pressure by effectively utilizing the brake fluid discharged from the wheel cylinder 5. Therefore, because the front wheel FR can be immediately controlled to an optimal slipstate, the braking distance can be shortened compared to normal antiskid control.
The structure described above can be adopted to a brake control apparatus shown in FIG. 19. In this case, the front and rear wheels have a reverse relationship in brake-fluid pressure against the brake control apparatus shown in FIG. 59. Further, two-way, two-port valve can be used as substitute for the proportional control valve 13. Moreover, the structure described above can be applied to a brake control apparatus in which wheel cylinders of a front-right wheel and front-left wheelare connected by a conduit. In this case, for example, when a driver brakes the vehicle during turning, the same effect as described above can be obtained by brake fluid movement from the wheel cylinder of an inner side wheel to the wheel cylinder of anouter side wheel.
An eighth embodiment will be described next, but description of portions similar to the embodiments described hereinabove will be simplified.
This embodiment provides an antiskid control system which differs from the foregoing seventh embodiment.
Firstly, basic structure of the brake control apparatus will be described with reference to the model diagram indicated in FIG. 18.
In FIG. 18, a brake pedal 1 is connected to a booster 2, and a master cylinder 3 is provided with a master reservoir 3a.
Master-cylinder pressure PU is conveyed by brake fluid within a first conduit A extending from the master cylinder 3 to first and second wheel cylinders 4 and 5. The master-cylinder pressure PU is similarly conveyed to a second conduit as well,but because structure similar to the first conduit A can be employed, detailed description will be omitted.
The first conduit A is made up of two parts separated by a pressure-amplifying device 10. Namely, the first conduit A has a first conduit part A1 to receive the master-cylinder pressure PU in the interval from the master cylinder 3 to thepressure-amplifying device 10. That is to say, a first conduit part A1 extends from the master cylinder 3 to the second wheel cylinder 5. The first conduit A also has a second conduit part A2 in the interval from the pressure-amplifying device 10 tothe first wheel cylinder 4.
The pressure-amplifying device 10 moves brake fluid of the first conduit part A1 to the second conduit part A2 and holds the pressure at the second conduit part A2 at second brake-fluid pressure PL when the brake pedal 1 is depressed and themaster-cylinder pressure PU is generated within the first conduit A. According to this embodiment, this pressure-amplifying device 10 is made up of a proportioning control valve (PV) 13 and a pump 15.
The pump 15 is connected to the first conduit A in parallel with the proportioning control valve 13, and takes in brake fluid from the first conduit part A1 and discharges brake fluid to the second conduit part A2 during generation of themaster-cylinder pressure PU.
The proportioning control valve 13 is connected to the first conduit A in a reverse direction. In a case where brake fluid from the first conduit part A1 has been moved to the second conduit part A2 by the pump 15 and the brake-fluid pressure ofthe second conduit part A2 has become the second brake-fluid pressure PL which is greater than the master-cylinder pressure PU, the proportioning control valve 13 acts to maintain this differential pressure (PL-PU). Additionally, a relief valve 17 isprovided in parallel with the proportioning control valve 13.
In this way, this embodiment is not provided with a antiskid control system, but by disposing the pressure-amplifying device 10 in the first conduit A together with connecting the proportioning control valve 13 in the reverse direction, the firstconduit part A1 on the low-pressure side and the second conduit part A2 on the high-pressure side are structured.
Consequently, because the second brake-fluid pressure PL of the second conduit part A2 which is higher in pressure than the master-cylinder pressure PU is applied to the first wheel cylinder 4, high pressure is imparted to the front-wheel side(i.e., to the front-right wheel FR) and high braking force can be demonstrated. Meanwhile, because the master-cylinder pressure PU of the first conduit part A1 which is lower in pressure than on the front-wheel side is applied to the rear-wheel side(i.e., to the rear-left wheel RL), susceptibility to the occurrence of locking is reduced.
That is to say, similarly to the above-described seventh embodiment, ideal braking-force distribution at the front and rear wheels is obtained. In other words, the brake-fluid pressure applied to the wheel cylinder 4 on the front-wheel side iscaused to be greater than the brake-fluid pressure applied to the wheel cylinder 5 on the rear-wheel side and brake-fluid pressure can be established at a high value overall. Therefore, braking force for the vehicle overall can be enhanced whiledemonstrating an effect of lessening depression force.
Additionally, because brake-fluid pressure higher than the master-cylinder pressure PU is applied to the front-wheel side and master-cylinder pressure PU is applied as-is to the rear-wheel side, there exists an effect wherein the wheel-cylinderpressure can be increased with maximum efficiency without causing any loss in the master-cylinder pressure PU.
In this embodiment, an example which does not dispose a proportioning control valve with respect to the second wheel cylinder 5 was described. However, a proportioning control valve may be connected to the second wheel cylinder 5 in the normaldirection as in the prior art. In this case, the difference between the brake-fluid pressure of the second wheel cylinder 5 and the brake-fluid pressure of the first wheel cylinder 4 can be caused to be still larger.
A ninth embodiment will be described next, but description of portions similar to the embodiments described hereinabove will be simplified.
This embodiment provides the basic structure of a brake control apparatus and an antiskid control system, similarly to the above-described seventh embodiment. However, a characteristic of the brake-fluid pressure applied to the first and secondwheel cylinders 4 and 5 is oppositely to the foregoing seventh embodiment at the front-wheel side and the rear-wheel side.
Firstly, basic structure of the brake control apparatus will be described with reference to the model diagram indicated in FIG. 19.
A brake pedal 1 is connected to a booster 2, and a master cylinder 3 is provided with a master reservoir 3a.
Master-cylinder pressure PU is conveyed by brake fluid within a first conduit A extending from the master cylinder 3 to first and second wheel cylinders 4 and 5. The master-cylinder pressure PU is similarly conveyed to a second conduit as well,but because structure similar to the first conduit A can be employed, detailed description will be omitted.
The first conduit A is made up of two parts separated by a pressure-amplifying device 10. That is to say, the first conduit A has a first conduit part A1 to receive the master-cylinder pressure PU in the interval from the master cylinder 3 tothe pressure-amplifying device 10 and a second conduit part A2 in the interval from the pressure-amplifying device 10 to the second wheel cylinder 5. Furthermore, the first conduit part A1 is provided with a first branching conduit part A1a extendingfrom the master cylinder 3 via a reservoir 20 to a pump 15, and a second branching conduit part A1b extending from the master cylinder 3 to the first wheel cylinder 4.
The pressure-amplifying device 10 moves brake fluid of the first conduit part A1 to the second conduit part A2 and holds the pressure in the second conduit part A2 at second brake-fluid pressure PL when the brake pedal 1 is depressed and themaster-cylinder pressure PU is generated within the first conduit A. According to this embodiment, this pressure-amplifying device 10, similarly to the foregoing seventh embodiment, is made up of the proportioning control valve (PV) 13 and the pump 15.
Additionally, a reservoir 20, first and second pressure-increasing control valves 31 and 32, first and second pressure-reducing control valves 33 and 34, and so on are also similar to the seventh embodiment.
In this way, according to this embodiment, the first conduit part A1 of the low-pressure side and the second conduit part A2 of the high-pressure side are structured by disposing the pressure-amplifying device 10 in the first conduit A andconnecting the proportioning control valve 13 in the reverse direction. Further, the first conduit part A1 is made up of the first branching conduit part A1a extending from the master cylinder 3 via the reservoir 20 to the pump 15, and the secondbranching conduit part A1b extending from the master cylinder 3 to the first wheel cylinder 4.
That is to say, oppositely to the foregoing seventh embodiment, the high-pressure second brake-fluid pressure PL is applied to the second wheel cylinder 5 and the master-cylinder pressure PU lower than the second brake-fluid pressure PL isapplied to the first wheel cylinder 4.
Consequently, because the second brake-fluid pressure PL which is higher in pressure than the master-cylinder pressure PU is applied to the second wheel cylinder 5, high pressure is imparted to the rear-wheel side (i.e., to the rear-left wheelRL); meanwhile, the master-cylinder pressure PU which is lower in pressure than on the rear-wheel side is applied the front-wheel side (i.e., to the front-right wheel FR).
This state is indicated in FIGS. 20A and 20B; in an example wherein a pressure-amplifying device 10 according to the present embodiment is absent and a proportioning control valve is connected in the normal direction with respect to the rear-leftwheel RL, the state of pressure of the front-right wheel FR and the rear-left wheel RL is such that both are suppressed to an equal to or lower level than the master-cylinder pressure PU, as shown in FIG. 20A. Meanwhile, according to the presentembodiment, the state of pressure of the front-right wheel FR and the rear-left wheel RL is such that, conversely to the case of the first embodiment indicated in FIG. 1, the pressure at the rear-left wheel RL is established at a higher level whilemaintaining the brake-fluid pressure in the first wheel cylinder 4 at the master-cylinder pressure PU, as shown in FIG. 20B.
Because the brake-fluid pressure applied to the wheel cylinder 5 on the rear-wheel side is caused to be greater than the brake-fluid pressure applied to the wheel cylinder 4 on the front-wheel side, brake-fluid pressure can be established at ahigh value overall, and so the braking force for the vehicle overall can be enhanced while demonstrating an effect of lessening depression force.
Particularly in a case of, for example, a large amount of cargo, load movement is small and large load weight is placed on the rear-wheel side during braking. According to this embodiment, the brake-fluid pressure of the wheel cylinder 5 on therear-wheel side is heightened and the braking force on the rear-wheel side can be increased, and so there exists the advantage that braking performance can be enhanced in a case of a large amount of cargo.
Moreover, the braking force on the front-wheel side is actually established to be greater than the braking force on the rear-wheel side due to the structure of the brake pads and the like, even in a case where the brake-fluid pressure applied tothe wheel cylinder 5 on the rear-wheel side has been caused to be larger than the brake-fluid pressure applied to the wheel cylinder 4 on the front-wheel side, as in this embodiment. Therefore, the rear-wheel can be prevented from falling prior to thefront-wheel into a locking state even in a case where load movement or the like has occurred during vehicle braking.
In this embodiment, an example provided with an antiskid control system was described, but this embodiment can be applied also in an example not provided with an antiskid control system, as in the above-described first embodiment. In this case,the matter of the brake-fluid pressure applied to the wheel cylinder on the rear-wheel side being caused to be larger than the brake-fluid pressure applied to the wheel cylinder on the front-wheel side differs from the foregoing first embodiment.
A tenth embodiment of the present invention will be described next with reference to FIG. 21.
The tenth embodiment combines an antiskid control system with the basic structure of a brake control apparatus; herein will be described an example wherein the brake control apparatus for a vehicle according to the present invention is applied ina vehicle of diagonal piping provided with respective conduits of connecting a front-right wheel cylinder and a rear-left wheel cylinder and of connecting a front-left wheel cylinder and a rear-right wheel cylinder in a front-wheel drive, four-wheeledvehicle.
Firstly, basic structure of the brake control apparatus will be described with reference to the model diagram indicated in FIG. 21. For structure exhibiting a mode of operation and effects similarly to the embodiments described hereinabove,symbols similar to the foregoing will be attached and description thereof will be simplified.
A first conduit A is made up of two parts separated by a pressure-amplifying device 10. Namely, the first conduit A has a first conduit part A1 to receive master-cylinder pressure PU in the interval from a master cylinder 3 to thepressure-amplifying device 10, and a second conduit part A2 in the interval from the pressure-amplifying device 10 to respective wheel cylinders 4 and 5.
The pressure-amplifying device 10 functions as a power brake which performs so-called brake assist; the pressure-amplifying device 10 moves brake fluid of the first conduit part A1 to the second conduit part A2 and holds the pressure at thesecond conduit part A2 at second brake-fluid pressure PL when the brake pedal 1 is depressed and the master-cylinder pressure PU is generated within the first conduit A.
According to the tenth embodiment, the pressure-amplifying device 10 is made up of a proportioning control valve (PV) 13 and a pump 15. In the structure of the first conduit A, the first conduit part | | | |
